FILE PHOTO - U.S. Secretary of State Rex Tillerson speaks on issues related to visas and travel after U.S. President Donald Trump signed a new travel ban order in Washington, U.S. on March 6, 2017. Credit: Kevin Lamarque/REUTERS

WASHINGTON - U.S. Secretary of State Rex Tillerson called on Iran and Russia on Tuesday to use their influence with the Syrian regime to make sure that it will not repeat its use of chemical weapons against its own citizens as part of the civil war currently raging in the country.

"We call upon Russia and Iran, yet again, to exercise their influence over the Syrian regime and to guarantee that this sort of horrific attack never happens again," said a statement by the State Department, attributed directly to Tillerson. He added that "Russia and Iran also bear great moral responsibility for these deaths," and that the Syria civil war "demands a genuine ceasefire."

The statement, which came after an alleged chemical attack killed at least 100 in northern Syria, also contained a strongly-worded condemnation of Assad's actions and came as a surprise amidst the Trump administration's verbally tough line against Iran thus far. Instead of calling on Iran to get out of the Syrian arena, it seemed to imply that Iran should use its influence inside Syria to restraint the Assad regime, which is a strategic ally of Tehran's.

"While we continue to monitor the terrible situation, it is clear that this is how Bashar al-Assad operates: with brutal, unabashed barbarism. Those who defend and support him, including Russia and Iran, should have no illusions about Assad or his intentions," Tillerson added. Just last week, however, two senior officials in the Trump administration - Press Secretary Sean Spicer and Ambassador Nikki Haley - said that Trump was not committed to taking down Assad's regime.

While Tillerson's comments pointed an unmistakable finger of blame at the Assad regime, another U.S. government source was even more direct, telling Reuters that the attack was "almost certainly" carried out by forces loyal to Assad. The source also said the U.S. government believes the chemical agent sarin was used in the attack.

Earlier Tuesday, the White House condemned the "heinous actions," but said the attack was a consequence of the Obama administration's "weakness." The statement added that there is not a fundamental option of "regime change" in Syria, calling the Assad government a "political reality."

It was believed that the attack was launched by a Sukhoi-type fighter aircraft, though there was no initial proof if the plane belonged to Russia or the Syrian government. However, locals in Idlib told Haaretz there was no doubt for anyone present that the Assad regime was responsible for the strike and that opposition forces even knew the identity of the pilot.